The technical field of invention relates to a leak detecting device for detecting presence of a gas. More particularly, the present invention pertains to a hand-held, single-hand-sized leak detecting device for general hazardous gas detection or air-borne sampling and detecting the presence of a specific gas.
Several different designs of leak detectors have been disclosed in various publications. The different designs are directed to provide potential solutions to particular problems. For example, US patent application publication no. US 2015/0028209 by Harju et al. (“Harju”), published Jan. 29, 2015, with assignee identified as Fieldpiece Instruments, Inc., discloses a refrigerant gas leak detector that incorporates a two-part unit—a first (handle) portion consisting of a gas sampling chamber and an infrared (IR) optical detector specific to detecting bandpass filtered IR energy within the range of 7 to 14 microns, and a second portion (presumably managed with the user's second hand, with the user's first hand holding the first/handle portion) connected to the first portion by a flexible tube, the second portion consisting of a suction pump, signal processing, and battery power components. The two-part design in Harju is disclosed as a solution to the problem of false triggering due IR emitter sensitivity to the vibration of the pump motor and to IR emitter sensitivity to pressure fluctuation from the pump. The two-part design places the IR emitter in the handle portion and the pump motor in the second portion, connected by three feet of flexible hosing, thereby dampening pump vibration and pressure fluctuation.
Harju also discloses an embodiment of an IR leak detector that utilizes a single housing for all the leak detector components—including the gas sampling chamber, the optical detector with bandpass filter for allowing IR energy within the range of 7 to 14 microns to pass (and attenuating energy outside of that range) between the IR emitter and IR sensor, the signal processing components, and (presumably, but not shown in figures or clearly described) the suction pump, and associated battery power. Harju discusses detection of refrigerants that absorb wavelengths of IR light primarily in the 8-10 micron range, and preferred detector designs having a 7 to 14 micron bandpass IR filter formed integrally with the IR sensor, which Harju discloses as being directed to the detection of refrigerants such as hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (FCFCs), and chlorofluorocarbons (CFCs).
Harju further discusses disclosures in Williams, I I et al. U.S. Pat. No. 7,022,993 and Williams, I I et al. U.S. Pat. No. 6,791,088 (collectively, “Williams”), both reexamined (with all claims in the '088 patent cancelled and claims 2-3, 6-7, and 9 determined patentable in the '993 patent) and having the assignee identified as Twin Rivers Engineering, Inc., that describe gas leak detector designs incorporating optical filtering to block IR energy that is absorbed by water vapor and other gases at wavelengths that are 6 microns and below, to reduce false triggering. The Williams gas leak detector designs include a (first) filter next to the IR emitter for blocking IR energy from approximately 6 microns down through the sampling chamber, and another (second) filter in front of the IR sensor for allowing a selected IR energy range of approximately 8 to approximately 10 microns to pass through the sampling chamber, with the IR sensor arranged for detecting resultant IR energy from the first filter and the second filter. Like Harju, Williams discloses designs directed to gas leak detection of HFCs, HCFCs, and CFCs. In addition, Williams lists numerous other compounds that can be detected, although Williams does not disclose the specific design changes needed for detection of such additional compounds. The additional compounds listed in Williams include: refrigerant blends, propane, methane, gasoline, ammonia, acetone, benzene, bromine, carbon dioxide, carbon monoxide, chlorine, fluorine, hydrogen sulfide, isobutyl alcohol, isopropyl ether, pentane, sulfur dioxide, sulfur hexafluoride, trichloroethane, vinyl acetate, vinyl bromide, and xylenes.
Both the Harju and Williams designs provide audible indication for gas leak detection. Harju includes a beeper that provides an audible signal when a leak is detected. The Williams design includes an audio output to the detector for emitting an audio signal from a detected leak, the audio output having a 1 Hz chirp rate that digitally shifts to a 2 Hz chirp rate upon detection of the gas leak. The chirp rate increases above the 2 Hz rate in proportion to the size of the gas leak being detected.
Both the Harju and Williams designs include gas leak detection by way of sensing a gas within a chamber between an IR emitter and an IR sensor/detector, with signals from the IR sensor/detector used to determine presence of a target gas to be detected. Harju discloses signal processing circuitry in very general terms that include circuitry for receiving and amplifying IR sensor output signals that are then input to a central processing unit (CPU). The CPU receives control signals from an external controls device and provides output signals to a display, status indicator lights, and to a beeper for an audible signal when a gas leak is detected. The Williams gas leak detector includes a signal detection accumulator in the detector with a forward biased detector circuit, and a zero circuit in the detector referenced to approximately a circuit ground instead of referenced between supply rails. Signals from the detection accumulator are directed to LED drivers for LED display and to a tone chirp rate generator for driving a piezo speaker.
Another IR instrument designed for the detection of contaminants in ambient air is the INFRARAN (trademark) specific vapor analyzer by Wilks Enterprise, Inc. (“Wilks”). The Wilks analyzer is a portable device and is larger (at 15″×7.3″×7.5″) and heavier (at 18 pounds) than either of the much smaller hand-held designs disclosed in Williams and Harju. Operation is two-handed, with one hand for carrying the 18 pound main body, and the other hand positioning an air sampling wand connected to a flexible tube leading back to the main body. The Wilks design provides an analyzer that can be purchased to measure a compound that has an absorption band in the IR range from 2.5 to 14.5 microns. The design uses fixed bandpass filters in the IR optics. An integral air pump draws the sample gas into a cell (chamber) having two mirrors, one on each of two opposite sides of the cell. An IR emitter and an IR detector are positioned aft of one of the mirrors on one side of the cell, with supporting amplifier and signal processing circuitry for receiving output from the IR detector, and a CPU, control inputs, display outputs, and (battery or AC) power management circuitry. The air pump draws the sample into the cell, and the sample absorbs the IR energy from the IR beam (that is bounced back and forth within the cell between the two mirrors). The IR detector measures the amount of energy absorbed at the selected wavelength, and the microprocessor converts it into a concentration (ppm or percent) for display. The Wilks product brochure lists the following as gases that can be detected and measured: acetone, carbon dioxide (absolute), carbon monoxide, carbon tetrachloride, desflurane, general hydrocarbons (hexane), isoflurane, isopropyl alcohol, methylene chloride, nitrous oxide, perchloroetylene, R 114, R 12, R 134A, R 236 fa, sevoflurane, sulfur hexafluoride, and toluene.
Each of the existing IR gas detector designs has disadvantages in terms of cost, complexity of design, ease of use, range of IR energy detected, method of audible alarm, form factor and ergonomics of the device, design aesthetics, and/or other factors. What is needed are designs for a hand-held, single-hand-sized leak detecting device for general hazardous gas detection or air-borne sampling and detecting the presence of a specific gas that address one or more disadvantage of existing designs.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.